1. Field of the Invention
The invention relates to a vehicle steering system in which there is no mechanical connection between a steering member operated for steering and a steering mechanism, and in which the steering mechanism is driven by a steered system motor.
2. Description of the Related Art
As a vehicle steering system, there has been proposed a steer-by-wire system in which there is no mechanical connection between a steering wheel that serves as a steering member and a steering mechanism, the turning angle of the steering wheel is detected by an angle sensor, and driving force generated by a steered system motor controlled based on an output from the angle sensor is transmitted to the steering mechanism. In such a steer-by-wire system, because there is no mechanical connection between the steering wheel and the steering mechanism, it is possible to prevent upthrust of the steering wheel in the event of a vehicle collision and it is possible to simplify the configuration of the steering mechanism and to reduce the weight of the vehicle. The flexibility in the arrangement of the steering wheel is increased. Further, operational components other than a steering wheel, such as a lever and a pedal, may be adopted. As described in Japanese Patent Application Publication No. 2012-1092 (JP 2012-1092 A), Japanese Patent Application Publication No. 2009-288872 (JP 2009-288872 A), Japanese Patent Application Publication No. 2008-213769 (JP 2008-213769 A), and Japanese Patent Application Publication No. 5-92769 (JP 5-92769 A), a steer-by-wire system is adopted in a material handling vehicle such as a forklift.
In a material handling vehicle such as a forklift in which a steer-by-wire system is adopted, the turning angle range of a steering wheel is larger than that of general vehicles. For example, in the material handling vehicle, the steering wheel may be turned by one turn or more to turn the vehicle. Therefore, in the material handling vehicle, an operation of returning steered wheels to the neutral position after turning the vehicle may place a heavy burden on an operator. This takes place also in general vehicles other than material handling vehicles in varying degrees.